1. Field of the Invention
Embodiments of the present invention generally relate to supporting substrates in processing chambers.
2. Description of the Related Art
During processing, substrates are positioned on a susceptor within a process chamber. The susceptor is supported by a susceptor support shaft, which is rotatable about a central axis. The susceptor support shaft includes multiple arms extending therefrom—usually three to six—which support the susceptor. As the susceptor support shaft is rotated during processing, the arms extending from the susceptor support shaft interrupt a pyrometer beam used to measure a temperature of the susceptor or the substrate. Even though the arms may be formed from quartz, which is generally optically transparent, at least some amount of light is absorbed by the arms, and thus, is not completely optically transparent. This amount of light absorbed by the arms affects the amount of light transmitted by the pyrometer beam to the susceptor, and thus, affects the accuracy of the temperature measurement by the pyrometer. As the susceptor support shaft rotates, there are periods when the arm is within the pyrometer beam path, and periods when the arm is adjacent to the pyrometer beam path. Thus, the amount of light from the pyrometer beam reaching the susceptor varies as the susceptor support rotates, resulting in periods of inaccurate temperature measurement.
Therefore, there is a need for an apparatus which allows more accurate temperature measurement.